diff options
Diffstat (limited to '')
| -rw-r--r-- | src/basic/fs-util.c | 1238 |
1 files changed, 1238 insertions, 0 deletions
diff --git a/src/basic/fs-util.c b/src/basic/fs-util.c new file mode 100644 index 0000000..9ba9268 --- /dev/null +++ b/src/basic/fs-util.c @@ -0,0 +1,1238 @@ +/* SPDX-License-Identifier: LGPL-2.1-or-later */ + +#include <errno.h> +#include <stddef.h> +#include <stdlib.h> +#include <sys/file.h> +#include <linux/falloc.h> +#include <linux/magic.h> +#include <unistd.h> + +#include "alloc-util.h" +#include "btrfs.h" +#include "dirent-util.h" +#include "fd-util.h" +#include "fileio.h" +#include "fs-util.h" +#include "hostname-util.h" +#include "label.h" +#include "lock-util.h" +#include "log.h" +#include "macro.h" +#include "missing_fcntl.h" +#include "missing_fs.h" +#include "missing_syscall.h" +#include "mkdir.h" +#include "parse-util.h" +#include "path-util.h" +#include "process-util.h" +#include "random-util.h" +#include "ratelimit.h" +#include "stat-util.h" +#include "stdio-util.h" +#include "string-util.h" +#include "strv.h" +#include "time-util.h" +#include "tmpfile-util.h" +#include "umask-util.h" +#include "user-util.h" + +int rmdir_parents(const char *path, const char *stop) { + char *p; + int r; + + assert(path); + assert(stop); + + if (!path_is_safe(path)) + return -EINVAL; + + if (!path_is_safe(stop)) + return -EINVAL; + + p = strdupa_safe(path); + + for (;;) { + char *slash = NULL; + + /* skip the last component. */ + r = path_find_last_component(p, /* accept_dot_dot= */ false, (const char **) &slash, NULL); + if (r <= 0) + return r; + if (slash == p) + return 0; + + assert(*slash == '/'); + *slash = '\0'; + + if (path_startswith_full(stop, p, /* accept_dot_dot= */ false)) + return 0; + + if (rmdir(p) < 0 && errno != ENOENT) + return -errno; + } +} + +int rename_noreplace(int olddirfd, const char *oldpath, int newdirfd, const char *newpath) { + int r; + + /* Try the ideal approach first */ + if (renameat2(olddirfd, oldpath, newdirfd, newpath, RENAME_NOREPLACE) >= 0) + return 0; + + /* renameat2() exists since Linux 3.15, btrfs and FAT added support for it later. If it is not implemented, + * fall back to a different method. */ + if (!ERRNO_IS_NOT_SUPPORTED(errno) && errno != EINVAL) + return -errno; + + /* Let's try to use linkat()+unlinkat() as fallback. This doesn't work on directories and on some file systems + * that do not support hard links (such as FAT, most prominently), but for files it's pretty close to what we + * want β though not atomic (i.e. for a short period both the new and the old filename will exist). */ + if (linkat(olddirfd, oldpath, newdirfd, newpath, 0) >= 0) { + + r = RET_NERRNO(unlinkat(olddirfd, oldpath, 0)); + if (r < 0) { + (void) unlinkat(newdirfd, newpath, 0); + return r; + } + + return 0; + } + + if (!ERRNO_IS_NOT_SUPPORTED(errno) && !IN_SET(errno, EINVAL, EPERM)) /* FAT returns EPERM on link()β¦ */ + return -errno; + + /* OK, neither RENAME_NOREPLACE nor linkat()+unlinkat() worked. Let's then fall back to the racy TOCTOU + * vulnerable accessat(F_OK) check followed by classic, replacing renameat(), we have nothing better. */ + + if (faccessat(newdirfd, newpath, F_OK, AT_SYMLINK_NOFOLLOW) >= 0) + return -EEXIST; + if (errno != ENOENT) + return -errno; + + return RET_NERRNO(renameat(olddirfd, oldpath, newdirfd, newpath)); +} + +int readlinkat_malloc(int fd, const char *p, char **ret) { + size_t l = PATH_MAX; + + assert(fd >= 0 || fd == AT_FDCWD); + + if (fd < 0 && isempty(p)) + return -EISDIR; /* In this case, the fd points to the current working directory, and is + * definitely not a symlink. Let's return earlier. */ + + for (;;) { + _cleanup_free_ char *c = NULL; + ssize_t n; + + c = new(char, l+1); + if (!c) + return -ENOMEM; + + n = readlinkat(fd, strempty(p), c, l); + if (n < 0) + return -errno; + + if ((size_t) n < l) { + c[n] = 0; + + if (ret) + *ret = TAKE_PTR(c); + + return 0; + } + + if (l > (SSIZE_MAX-1)/2) /* readlinkat() returns an ssize_t, and we want an extra byte for a + * trailing NUL, hence do an overflow check relative to SSIZE_MAX-1 + * here */ + return -EFBIG; + + l *= 2; + } +} + +int readlink_malloc(const char *p, char **ret) { + return readlinkat_malloc(AT_FDCWD, p, ret); +} + +int readlink_value(const char *p, char **ret) { + _cleanup_free_ char *link = NULL, *name = NULL; + int r; + + assert(p); + assert(ret); + + r = readlink_malloc(p, &link); + if (r < 0) + return r; + + r = path_extract_filename(link, &name); + if (r < 0) + return r; + if (r == O_DIRECTORY) + return -EINVAL; + + *ret = TAKE_PTR(name); + return 0; +} + +int readlink_and_make_absolute(const char *p, char **ret) { + _cleanup_free_ char *target = NULL; + int r; + + assert(p); + assert(ret); + + r = readlink_malloc(p, &target); + if (r < 0) + return r; + + return file_in_same_dir(p, target, ret); +} + +int chmod_and_chown_at(int dir_fd, const char *path, mode_t mode, uid_t uid, gid_t gid) { + _cleanup_close_ int fd = -EBADF; + + assert(dir_fd >= 0 || dir_fd == AT_FDCWD); + + if (path) { + /* Let's acquire an O_PATH fd, as precaution to change mode/owner on the same file */ + fd = openat(dir_fd, path, O_PATH|O_CLOEXEC|O_NOFOLLOW); + if (fd < 0) + return -errno; + dir_fd = fd; + + } else if (dir_fd == AT_FDCWD) { + /* Let's acquire an O_PATH fd of the current directory */ + fd = openat(dir_fd, ".", O_PATH|O_CLOEXEC|O_NOFOLLOW|O_DIRECTORY); + if (fd < 0) + return -errno; + dir_fd = fd; + } + + return fchmod_and_chown(dir_fd, mode, uid, gid); +} + +int fchmod_and_chown_with_fallback(int fd, const char *path, mode_t mode, uid_t uid, gid_t gid) { + bool do_chown, do_chmod; + struct stat st; + int r; + + /* Change ownership and access mode of the specified fd. Tries to do so safely, ensuring that at no + * point in time the access mode is above the old access mode under the old ownership or the new + * access mode under the new ownership. Note: this call tries hard to leave the access mode + * unaffected if the uid/gid is changed, i.e. it undoes implicit suid/sgid dropping the kernel does + * on chown(). + * + * This call is happy with O_PATH fds. + * + * If path is given, allow a fallback path which does not use /proc/self/fd/. On any normal system + * /proc will be mounted, but in certain improperly assembled environments it might not be. This is + * less secure (potential TOCTOU), so should only be used after consideration. */ + + if (fstat(fd, &st) < 0) + return -errno; + + do_chown = + (uid != UID_INVALID && st.st_uid != uid) || + (gid != GID_INVALID && st.st_gid != gid); + + do_chmod = + !S_ISLNK(st.st_mode) && /* chmod is not defined on symlinks */ + ((mode != MODE_INVALID && ((st.st_mode ^ mode) & 07777) != 0) || + do_chown); /* If we change ownership, make sure we reset the mode afterwards, since chown() + * modifies the access mode too */ + + if (mode == MODE_INVALID) + mode = st.st_mode; /* If we only shall do a chown(), save original mode, since chown() might break it. */ + else if ((mode & S_IFMT) != 0 && ((mode ^ st.st_mode) & S_IFMT) != 0) + return -EINVAL; /* insist on the right file type if it was specified */ + + if (do_chown && do_chmod) { + mode_t minimal = st.st_mode & mode; /* the subset of the old and the new mask */ + + if (((minimal ^ st.st_mode) & 07777) != 0) { + r = fchmod_opath(fd, minimal & 07777); + if (r < 0) { + if (!path || r != -ENOSYS) + return r; + + /* Fallback path which doesn't use /proc/self/fd/. */ + if (chmod(path, minimal & 07777) < 0) + return -errno; + } + } + } + + if (do_chown) + if (fchownat(fd, "", uid, gid, AT_EMPTY_PATH) < 0) + return -errno; + + if (do_chmod) { + r = fchmod_opath(fd, mode & 07777); + if (r < 0) { + if (!path || r != -ENOSYS) + return r; + + /* Fallback path which doesn't use /proc/self/fd/. */ + if (chmod(path, mode & 07777) < 0) + return -errno; + } + } + + return do_chown || do_chmod; +} + +int fchmod_umask(int fd, mode_t m) { + _cleanup_umask_ mode_t u = umask(0777); + + return RET_NERRNO(fchmod(fd, m & (~u))); +} + +int fchmod_opath(int fd, mode_t m) { + /* This function operates also on fd that might have been opened with + * O_PATH. The tool set we have is non-intuitive: + * - fchmod(2) only operates on open files (i. e., fds with an open file description); + * - fchmodat(2) does not have a flag arg like fchownat(2) does, so no way to pass AT_EMPTY_PATH; + * + it should not be confused with the libc fchmodat(3) interface, which adds 4th flag argument, + * but does not support AT_EMPTY_PATH (only supports AT_SYMLINK_NOFOLLOW); + * - fchmodat2(2) supports all the AT_* flags, but is still very recent. + * + * We try to use fchmodat2(), and, if it is not supported, resort + * to the /proc/self/fd dance. */ + + assert(fd >= 0); + + if (fchmodat2(fd, "", m, AT_EMPTY_PATH) >= 0) + return 0; + if (!IN_SET(errno, ENOSYS, EPERM)) /* Some container managers block unknown syscalls with EPERM */ + return -errno; + + if (chmod(FORMAT_PROC_FD_PATH(fd), m) < 0) { + if (errno != ENOENT) + return -errno; + + if (proc_mounted() == 0) + return -ENOSYS; /* if we have no /proc/, the concept is not implementable */ + + return -ENOENT; + } + + return 0; +} + +int futimens_opath(int fd, const struct timespec ts[2]) { + /* Similar to fchmod_opath() but for futimens() */ + + if (utimensat(AT_FDCWD, FORMAT_PROC_FD_PATH(fd), ts, 0) < 0) { + if (errno != ENOENT) + return -errno; + + if (proc_mounted() == 0) + return -ENOSYS; /* if we have no /proc/, the concept is not implementable */ + + return -ENOENT; + } + + return 0; +} + +int stat_warn_permissions(const char *path, const struct stat *st) { + assert(path); + assert(st); + + /* Don't complain if we are reading something that is not a file, for example /dev/null */ + if (!S_ISREG(st->st_mode)) + return 0; + + if (st->st_mode & 0111) + log_warning("Configuration file %s is marked executable. Please remove executable permission bits. Proceeding anyway.", path); + + if (st->st_mode & 0002) + log_warning("Configuration file %s is marked world-writable. Please remove world writability permission bits. Proceeding anyway.", path); + + if (getpid_cached() == 1 && (st->st_mode & 0044) != 0044) + log_warning("Configuration file %s is marked world-inaccessible. This has no effect as configuration data is accessible via APIs without restrictions. Proceeding anyway.", path); + + return 0; +} + +int fd_warn_permissions(const char *path, int fd) { + struct stat st; + + assert(path); + assert(fd >= 0); + + if (fstat(fd, &st) < 0) + return -errno; + + return stat_warn_permissions(path, &st); +} + +int touch_file(const char *path, bool parents, usec_t stamp, uid_t uid, gid_t gid, mode_t mode) { + _cleanup_close_ int fd = -EBADF; + int r, ret; + + assert(path); + + /* Note that touch_file() does not follow symlinks: if invoked on an existing symlink, then it is the symlink + * itself which is updated, not its target + * + * Returns the first error we encounter, but tries to apply as much as possible. */ + + if (parents) + (void) mkdir_parents(path, 0755); + + /* Initially, we try to open the node with O_PATH, so that we get a reference to the node. This is useful in + * case the path refers to an existing device or socket node, as we can open it successfully in all cases, and + * won't trigger any driver magic or so. */ + fd = open(path, O_PATH|O_CLOEXEC|O_NOFOLLOW); + if (fd < 0) { + if (errno != ENOENT) + return -errno; + + /* if the node doesn't exist yet, we create it, but with O_EXCL, so that we only create a regular file + * here, and nothing else */ + fd = open(path, O_WRONLY|O_CREAT|O_EXCL|O_CLOEXEC, IN_SET(mode, 0, MODE_INVALID) ? 0644 : mode); + if (fd < 0) + return -errno; + } + + /* Let's make a path from the fd, and operate on that. With this logic, we can adjust the access mode, + * ownership and time of the file node in all cases, even if the fd refers to an O_PATH object β which is + * something fchown(), fchmod(), futimensat() don't allow. */ + ret = fchmod_and_chown(fd, mode, uid, gid); + + if (stamp != USEC_INFINITY) { + struct timespec ts[2]; + + timespec_store(&ts[0], stamp); + ts[1] = ts[0]; + r = futimens_opath(fd, ts); + } else + r = futimens_opath(fd, NULL); + if (r < 0 && ret >= 0) + return r; + + return ret; +} + +int symlink_idempotent(const char *from, const char *to, bool make_relative) { + _cleanup_free_ char *relpath = NULL; + int r; + + assert(from); + assert(to); + + if (make_relative) { + r = path_make_relative_parent(to, from, &relpath); + if (r < 0) + return r; + + from = relpath; + } + + if (symlink(from, to) < 0) { + _cleanup_free_ char *p = NULL; + + if (errno != EEXIST) + return -errno; + + r = readlink_malloc(to, &p); + if (r == -EINVAL) /* Not a symlink? In that case return the original error we encountered: -EEXIST */ + return -EEXIST; + if (r < 0) /* Any other error? In that case propagate it as is */ + return r; + + if (!streq(p, from)) /* Not the symlink we want it to be? In that case, propagate the original -EEXIST */ + return -EEXIST; + } + + return 0; +} + +int symlinkat_atomic_full(const char *from, int atfd, const char *to, bool make_relative) { + _cleanup_free_ char *relpath = NULL, *t = NULL; + int r; + + assert(from); + assert(to); + + if (make_relative) { + r = path_make_relative_parent(to, from, &relpath); + if (r < 0) + return r; + + from = relpath; + } + + r = tempfn_random(to, NULL, &t); + if (r < 0) + return r; + + if (symlinkat(from, atfd, t) < 0) + return -errno; + + r = RET_NERRNO(renameat(atfd, t, atfd, to)); + if (r < 0) { + (void) unlinkat(atfd, t, 0); + return r; + } + + return 0; +} + +int mknodat_atomic(int atfd, const char *path, mode_t mode, dev_t dev) { + _cleanup_free_ char *t = NULL; + int r; + + assert(path); + + r = tempfn_random(path, NULL, &t); + if (r < 0) + return r; + + if (mknodat(atfd, t, mode, dev) < 0) + return -errno; + + r = RET_NERRNO(renameat(atfd, t, atfd, path)); + if (r < 0) { + (void) unlinkat(atfd, t, 0); + return r; + } + + return 0; +} + +int mkfifoat_atomic(int atfd, const char *path, mode_t mode) { + _cleanup_free_ char *t = NULL; + int r; + + assert(path); + + /* We're only interested in the (random) filename. */ + r = tempfn_random(path, NULL, &t); + if (r < 0) + return r; + + if (mkfifoat(atfd, t, mode) < 0) + return -errno; + + r = RET_NERRNO(renameat(atfd, t, atfd, path)); + if (r < 0) { + (void) unlinkat(atfd, t, 0); + return r; + } + + return 0; +} + +int get_files_in_directory(const char *path, char ***list) { + _cleanup_strv_free_ char **l = NULL; + _cleanup_closedir_ DIR *d = NULL; + size_t n = 0; + + assert(path); + + /* Returns all files in a directory in *list, and the number + * of files as return value. If list is NULL returns only the + * number. */ + + d = opendir(path); + if (!d) + return -errno; + + FOREACH_DIRENT_ALL(de, d, return -errno) { + if (!dirent_is_file(de)) + continue; + + if (list) { + /* one extra slot is needed for the terminating NULL */ + if (!GREEDY_REALLOC(l, n + 2)) + return -ENOMEM; + + l[n] = strdup(de->d_name); + if (!l[n]) + return -ENOMEM; + + l[++n] = NULL; + } else + n++; + } + + if (list) + *list = TAKE_PTR(l); + + return n; +} + +static int getenv_tmp_dir(const char **ret_path) { + int r, ret = 0; + + assert(ret_path); + + /* We use the same order of environment variables python uses in tempfile.gettempdir(): + * https://docs.python.org/3/library/tempfile.html#tempfile.gettempdir */ + FOREACH_STRING(n, "TMPDIR", "TEMP", "TMP") { + const char *e; + + e = secure_getenv(n); + if (!e) + continue; + if (!path_is_absolute(e)) { + r = -ENOTDIR; + goto next; + } + if (!path_is_normalized(e)) { + r = -EPERM; + goto next; + } + + r = is_dir(e, true); + if (r < 0) + goto next; + if (r == 0) { + r = -ENOTDIR; + goto next; + } + + *ret_path = e; + return 1; + + next: + /* Remember first error, to make this more debuggable */ + if (ret >= 0) + ret = r; + } + + if (ret < 0) + return ret; + + *ret_path = NULL; + return ret; +} + +static int tmp_dir_internal(const char *def, const char **ret) { + const char *e; + int r, k; + + assert(def); + assert(ret); + + r = getenv_tmp_dir(&e); + if (r > 0) { + *ret = e; + return 0; + } + + k = is_dir(def, true); + if (k == 0) + k = -ENOTDIR; + if (k < 0) + return r < 0 ? r : k; + + *ret = def; + return 0; +} + +int var_tmp_dir(const char **ret) { + + /* Returns the location for "larger" temporary files, that is backed by physical storage if available, and thus + * even might survive a boot: /var/tmp. If $TMPDIR (or related environment variables) are set, its value is + * returned preferably however. Note that both this function and tmp_dir() below are affected by $TMPDIR, + * making it a variable that overrides all temporary file storage locations. */ + + return tmp_dir_internal("/var/tmp", ret); +} + +int tmp_dir(const char **ret) { + + /* Similar to var_tmp_dir() above, but returns the location for "smaller" temporary files, which is usually + * backed by an in-memory file system: /tmp. */ + + return tmp_dir_internal("/tmp", ret); +} + +int unlink_or_warn(const char *filename) { + if (unlink(filename) < 0 && errno != ENOENT) + /* If the file doesn't exist and the fs simply was read-only (in which + * case unlink() returns EROFS even if the file doesn't exist), don't + * complain */ + if (errno != EROFS || access(filename, F_OK) >= 0) + return log_error_errno(errno, "Failed to remove \"%s\": %m", filename); + + return 0; +} + +int access_fd(int fd, int mode) { + /* Like access() but operates on an already open fd */ + + if (access(FORMAT_PROC_FD_PATH(fd), mode) < 0) { + if (errno != ENOENT) + return -errno; + + /* ENOENT can mean two things: that the fd does not exist or that /proc is not mounted. Let's + * make things debuggable and distinguish the two. */ + + if (proc_mounted() == 0) + return -ENOSYS; /* /proc is not available or not set up properly, we're most likely in some chroot + * environment. */ + + return -EBADF; /* The directory exists, hence it's the fd that doesn't. */ + } + + return 0; +} + +void unlink_tempfilep(char (*p)[]) { + /* If the file is created with mkstemp(), it will (almost always) + * change the suffix. Treat this as a sign that the file was + * successfully created. We ignore both the rare case where the + * original suffix is used and unlink failures. */ + if (!endswith(*p, ".XXXXXX")) + (void) unlink(*p); +} + +int unlinkat_deallocate(int fd, const char *name, UnlinkDeallocateFlags flags) { + _cleanup_close_ int truncate_fd = -EBADF; + struct stat st; + off_t l, bs; + + assert((flags & ~(UNLINK_REMOVEDIR|UNLINK_ERASE)) == 0); + + /* Operates like unlinkat() but also deallocates the file contents if it is a regular file and there's no other + * link to it. This is useful to ensure that other processes that might have the file open for reading won't be + * able to keep the data pinned on disk forever. This call is particular useful whenever we execute clean-up + * jobs ("vacuuming"), where we want to make sure the data is really gone and the disk space released and + * returned to the free pool. + * + * Deallocation is preferably done by FALLOC_FL_PUNCH_HOLE|FALLOC_FL_KEEP_SIZE (π) if supported, which means + * the file won't change size. That's a good thing since we shouldn't needlessly trigger SIGBUS in other + * programs that have mmap()ed the file. (The assumption here is that changing file contents to all zeroes + * underneath those programs is the better choice than simply triggering SIGBUS in them which truncation does.) + * However if hole punching is not implemented in the kernel or file system we'll fall back to normal file + * truncation (πͺ), as our goal of deallocating the data space trumps our goal of being nice to readers (π). + * + * Note that we attempt deallocation, but failure to succeed with that is not considered fatal, as long as the + * primary job β to delete the file β is accomplished. */ + + if (!FLAGS_SET(flags, UNLINK_REMOVEDIR)) { + truncate_fd = openat(fd, name, O_WRONLY|O_CLOEXEC|O_NOCTTY|O_NOFOLLOW|O_NONBLOCK); + if (truncate_fd < 0) { + + /* If this failed because the file doesn't exist propagate the error right-away. Also, + * AT_REMOVEDIR wasn't set, and we tried to open the file for writing, which means EISDIR is + * returned when this is a directory but we are not supposed to delete those, hence propagate + * the error right-away too. */ + if (IN_SET(errno, ENOENT, EISDIR)) + return -errno; + + if (errno != ELOOP) /* don't complain if this is a symlink */ + log_debug_errno(errno, "Failed to open file '%s' for deallocation, ignoring: %m", name); + } + } + + if (unlinkat(fd, name, FLAGS_SET(flags, UNLINK_REMOVEDIR) ? AT_REMOVEDIR : 0) < 0) + return -errno; + + if (truncate_fd < 0) /* Don't have a file handle, can't do more βΉοΈ */ + return 0; + + if (fstat(truncate_fd, &st) < 0) { + log_debug_errno(errno, "Failed to stat file '%s' for deallocation, ignoring: %m", name); + return 0; + } + + if (!S_ISREG(st.st_mode)) + return 0; + + if (FLAGS_SET(flags, UNLINK_ERASE) && st.st_size > 0 && st.st_nlink == 0) { + uint64_t left = st.st_size; + char buffer[64 * 1024]; + + /* If erasing is requested, let's overwrite the file with random data once before deleting + * it. This isn't going to give you shred(1) semantics, but hopefully should be good enough + * for stuff backed by tmpfs at least. + * + * Note that we only erase like this if the link count of the file is zero. If it is higher it + * is still linked by someone else and we'll leave it to them to remove it securely + * eventually! */ + + random_bytes(buffer, sizeof(buffer)); + + while (left > 0) { + ssize_t n; + + n = write(truncate_fd, buffer, MIN(sizeof(buffer), left)); + if (n < 0) { + log_debug_errno(errno, "Failed to erase data in file '%s', ignoring.", name); + break; + } + + assert(left >= (size_t) n); + left -= n; + } + + /* Let's refresh metadata */ + if (fstat(truncate_fd, &st) < 0) { + log_debug_errno(errno, "Failed to stat file '%s' for deallocation, ignoring: %m", name); + return 0; + } + } + + /* Don't dallocate if there's nothing to deallocate or if the file is linked elsewhere */ + if (st.st_blocks == 0 || st.st_nlink > 0) + return 0; + + /* If this is a regular file, it actually took up space on disk and there are no other links it's time to + * punch-hole/truncate this to release the disk space. */ + + bs = MAX(st.st_blksize, 512); + l = ROUND_UP(st.st_size, bs); /* Round up to next block size */ + + if (fallocate(truncate_fd, FALLOC_FL_PUNCH_HOLE|FALLOC_FL_KEEP_SIZE, 0, l) >= 0) + return 0; /* Successfully punched a hole! π */ + + /* Fall back to truncation */ + if (ftruncate(truncate_fd, 0) < 0) { + log_debug_errno(errno, "Failed to truncate file to 0, ignoring: %m"); + return 0; + } + + return 0; +} + +int open_parent_at(int dir_fd, const char *path, int flags, mode_t mode) { + _cleanup_free_ char *parent = NULL; + int r; + + assert(dir_fd >= 0 || dir_fd == AT_FDCWD); + assert(path); + + r = path_extract_directory(path, &parent); + if (r == -EDESTADDRREQ) { + parent = strdup("."); + if (!parent) + return -ENOMEM; + } else if (r == -EADDRNOTAVAIL) { + parent = strdup(path); + if (!parent) + return -ENOMEM; + } else if (r < 0) + return r; + + /* Let's insist on O_DIRECTORY since the parent of a file or directory is a directory. Except if we open an + * O_TMPFILE file, because in that case we are actually create a regular file below the parent directory. */ + + if (FLAGS_SET(flags, O_PATH)) + flags |= O_DIRECTORY; + else if (!FLAGS_SET(flags, O_TMPFILE)) + flags |= O_DIRECTORY|O_RDONLY; + + return RET_NERRNO(openat(dir_fd, parent, flags, mode)); +} + +int conservative_renameat( + int olddirfd, const char *oldpath, + int newdirfd, const char *newpath) { + + _cleanup_close_ int old_fd = -EBADF, new_fd = -EBADF; + struct stat old_stat, new_stat; + + /* Renames the old path to the new path, much like renameat() β except if both are regular files and + * have the exact same contents and basic file attributes already. In that case remove the new file + * instead. This call is useful for reducing inotify wakeups on files that are updated but don't + * actually change. This function is written in a style that we rather rename too often than suppress + * too much. I.e. whenever we are in doubt, we rather rename than fail. After all reducing inotify + * events is an optimization only, not more. */ + + old_fd = openat(olddirfd, oldpath, O_CLOEXEC|O_RDONLY|O_NOCTTY|O_NOFOLLOW); + if (old_fd < 0) + goto do_rename; + + new_fd = openat(newdirfd, newpath, O_CLOEXEC|O_RDONLY|O_NOCTTY|O_NOFOLLOW); + if (new_fd < 0) + goto do_rename; + + if (fstat(old_fd, &old_stat) < 0) + goto do_rename; + + if (!S_ISREG(old_stat.st_mode)) + goto do_rename; + + if (fstat(new_fd, &new_stat) < 0) + goto do_rename; + + if (stat_inode_same(&new_stat, &old_stat)) + goto is_same; + + if (old_stat.st_mode != new_stat.st_mode || + old_stat.st_size != new_stat.st_size || + old_stat.st_uid != new_stat.st_uid || + old_stat.st_gid != new_stat.st_gid) + goto do_rename; + + for (;;) { + uint8_t buf1[16*1024]; + uint8_t buf2[sizeof(buf1)]; + ssize_t l1, l2; + + l1 = read(old_fd, buf1, sizeof(buf1)); + if (l1 < 0) + goto do_rename; + + if (l1 == sizeof(buf1)) + /* Read the full block, hence read a full block in the other file too */ + + l2 = read(new_fd, buf2, l1); + else { + assert((size_t) l1 < sizeof(buf1)); + + /* Short read. This hence was the last block in the first file, and then came + * EOF. Read one byte more in the second file, so that we can verify we hit EOF there + * too. */ + + assert((size_t) (l1 + 1) <= sizeof(buf2)); + l2 = read(new_fd, buf2, l1 + 1); + } + if (l2 != l1) + goto do_rename; + + if (memcmp(buf1, buf2, l1) != 0) + goto do_rename; + + if ((size_t) l1 < sizeof(buf1)) /* We hit EOF on the first file, and the second file too, hence exit + * now. */ + break; + } + +is_same: + /* Everything matches? Then don't rename, instead remove the source file, and leave the existing + * destination in place */ + + if (unlinkat(olddirfd, oldpath, 0) < 0) + goto do_rename; + + return 0; + +do_rename: + if (renameat(olddirfd, oldpath, newdirfd, newpath) < 0) + return -errno; + + return 1; +} + +int posix_fallocate_loop(int fd, uint64_t offset, uint64_t size) { + RateLimit rl; + int r; + + r = posix_fallocate(fd, offset, size); /* returns positive errnos on error */ + if (r != EINTR) + return -r; /* Let's return negative errnos, like common in our codebase */ + + /* On EINTR try a couple of times more, but protect against busy looping + * (not more than 16 times per 10s) */ + rl = (const RateLimit) { 10 * USEC_PER_SEC, 16 }; + while (ratelimit_below(&rl)) { + r = posix_fallocate(fd, offset, size); + if (r != EINTR) + return -r; + } + + return -EINTR; +} + +int parse_cifs_service( + const char *s, + char **ret_host, + char **ret_service, + char **ret_path) { + + _cleanup_free_ char *h = NULL, *ss = NULL, *x = NULL; + const char *p, *e, *d; + char delimiter; + + /* Parses a CIFS service in form of //host/service/pathβ¦ and splitting it in three parts. The last + * part is optional, in which case NULL is returned there. To maximize compatibility syntax with + * backslashes instead of slashes is accepted too. */ + + if (!s) + return -EINVAL; + + p = startswith(s, "//"); + if (!p) { + p = startswith(s, "\\\\"); + if (!p) + return -EINVAL; + } + + delimiter = s[0]; + e = strchr(p, delimiter); + if (!e) + return -EINVAL; + + h = strndup(p, e - p); + if (!h) + return -ENOMEM; + + if (!hostname_is_valid(h, 0)) + return -EINVAL; + + e++; + + d = strchrnul(e, delimiter); + + ss = strndup(e, d - e); + if (!ss) + return -ENOMEM; + + if (!filename_is_valid(ss)) + return -EINVAL; + + if (!isempty(d)) { + x = strdup(skip_leading_chars(d, CHAR_TO_STR(delimiter))); + if (!x) + return -EINVAL; + + /* Make sure to convert Windows-style "\" β Unix-style / */ + for (char *i = x; *i; i++) + if (*i == delimiter) + *i = '/'; + + if (!path_is_valid(x)) + return -EINVAL; + + path_simplify(x); + if (!path_is_normalized(x)) + return -EINVAL; + } + + if (ret_host) + *ret_host = TAKE_PTR(h); + if (ret_service) + *ret_service = TAKE_PTR(ss); + if (ret_path) + *ret_path = TAKE_PTR(x); + + return 0; +} + +int open_mkdir_at(int dirfd, const char *path, int flags, mode_t mode) { + _cleanup_close_ int fd = -EBADF, parent_fd = -EBADF; + _cleanup_free_ char *fname = NULL, *parent = NULL; + int r; + + /* Creates a directory with mkdirat() and then opens it, in the "most atomic" fashion we can + * do. Guarantees that the returned fd refers to a directory. If O_EXCL is specified will fail if the + * dir already exists. Otherwise will open an existing dir, but only if it is one. */ + + if (flags & ~(O_RDONLY|O_CLOEXEC|O_DIRECTORY|O_EXCL|O_NOATIME|O_NOFOLLOW|O_PATH)) + return -EINVAL; + if ((flags & O_ACCMODE) != O_RDONLY) + return -EINVAL; + + /* Note that O_DIRECTORY|O_NOFOLLOW is implied, but we allow specifying it anyway. The following + * flags actually make sense to specify: O_CLOEXEC, O_EXCL, O_NOATIME, O_PATH */ + + /* If this is not a valid filename, it's a path. Let's open the parent directory then, so + * that we can pin it, and operate below it. */ + r = path_extract_directory(path, &parent); + if (r < 0) { + if (!IN_SET(r, -EDESTADDRREQ, -EADDRNOTAVAIL)) + return r; + } else { + r = path_extract_filename(path, &fname); + if (r < 0) + return r; + + parent_fd = openat(dirfd, parent, O_PATH|O_DIRECTORY|O_CLOEXEC); + if (parent_fd < 0) + return -errno; + + dirfd = parent_fd; + path = fname; + } + + fd = xopenat(dirfd, path, flags|O_CREAT|O_DIRECTORY|O_NOFOLLOW, /* xopen_flags = */ 0, mode); + if (IN_SET(fd, -ELOOP, -ENOTDIR)) + return -EEXIST; + if (fd < 0) + return fd; + + return TAKE_FD(fd); +} + +int openat_report_new(int dirfd, const char *pathname, int flags, mode_t mode, bool *ret_newly_created) { + unsigned attempts = 7; + int fd; + + /* Just like openat(), but adds one thing: optionally returns whether we created the file anew or if + * it already existed before. This is only relevant if O_CREAT is set without O_EXCL, and thus will + * shortcut to openat() otherwise */ + + if (!ret_newly_created) + return RET_NERRNO(openat(dirfd, pathname, flags, mode)); + + if (!FLAGS_SET(flags, O_CREAT) || FLAGS_SET(flags, O_EXCL)) { + fd = openat(dirfd, pathname, flags, mode); + if (fd < 0) + return -errno; + + *ret_newly_created = FLAGS_SET(flags, O_CREAT); + return fd; + } + + for (;;) { + /* First, attempt to open without O_CREAT/O_EXCL, i.e. open existing file */ + fd = openat(dirfd, pathname, flags & ~(O_CREAT | O_EXCL), mode); + if (fd >= 0) { + *ret_newly_created = false; + return fd; + } + if (errno != ENOENT) + return -errno; + + /* So the file didn't exist yet, hence create it with O_CREAT/O_EXCL. */ + fd = openat(dirfd, pathname, flags | O_CREAT | O_EXCL, mode); + if (fd >= 0) { + *ret_newly_created = true; + return fd; + } + if (errno != EEXIST) + return -errno; + + /* Hmm, so now we got EEXIST? So it apparently exists now? If so, let's try to open again + * without the two flags. But let's not spin forever, hence put a limit on things */ + + if (--attempts == 0) /* Give up eventually, somebody is playing with us */ + return -EEXIST; + } +} + +int xopenat(int dir_fd, const char *path, int open_flags, XOpenFlags xopen_flags, mode_t mode) { + _cleanup_close_ int fd = -EBADF; + bool made = false; + int r; + + assert(dir_fd >= 0 || dir_fd == AT_FDCWD); + + /* This is like openat(), but has a few tricks up its sleeves, extending behaviour: + * + * β’ O_DIRECTORY|O_CREAT is supported, which causes a directory to be created, and immediately + * opened. When used with the XO_SUBVOLUME flag this will even create a btrfs subvolume. + * + * β’ If O_CREAT is used with XO_LABEL, any created file will be immediately relabelled. + * + * β’ If the path is specified NULL or empty, behaves like fd_reopen(). + */ + + if (isempty(path)) { + assert(!FLAGS_SET(open_flags, O_CREAT|O_EXCL)); + return fd_reopen(dir_fd, open_flags & ~O_NOFOLLOW); + } + + if (FLAGS_SET(open_flags, O_CREAT) && FLAGS_SET(xopen_flags, XO_LABEL)) { + r = label_ops_pre(dir_fd, path, FLAGS_SET(open_flags, O_DIRECTORY) ? S_IFDIR : S_IFREG); + if (r < 0) + return r; + } + + if (FLAGS_SET(open_flags, O_DIRECTORY|O_CREAT)) { + if (FLAGS_SET(xopen_flags, XO_SUBVOLUME)) + r = btrfs_subvol_make_fallback(dir_fd, path, mode); + else + r = RET_NERRNO(mkdirat(dir_fd, path, mode)); + if (r == -EEXIST) { + if (FLAGS_SET(open_flags, O_EXCL)) + return -EEXIST; + + made = false; + } else if (r < 0) + return r; + else + made = true; + + if (FLAGS_SET(xopen_flags, XO_LABEL)) { + r = label_ops_post(dir_fd, path); + if (r < 0) + return r; + } + + open_flags &= ~(O_EXCL|O_CREAT); + xopen_flags &= ~XO_LABEL; + } + + fd = RET_NERRNO(openat(dir_fd, path, open_flags, mode)); + if (fd < 0) { + if (IN_SET(fd, + /* We got ENOENT? then someone else immediately removed it after we + * created it. In that case let's return immediately without unlinking + * anything, because there simply isn't anything to unlink anymore. */ + -ENOENT, + /* is a symlink? exists already β created by someone else, don't unlink */ + -ELOOP, + /* not a directory? exists already β created by someone else, don't unlink */ + -ENOTDIR)) + return fd; + + if (made) + (void) unlinkat(dir_fd, path, AT_REMOVEDIR); + + return fd; + } + + if (FLAGS_SET(open_flags, O_CREAT) && FLAGS_SET(xopen_flags, XO_LABEL)) { + r = label_ops_post(dir_fd, path); + if (r < 0) + return r; + } + + return TAKE_FD(fd); +} + +int xopenat_lock( + int dir_fd, + const char *path, + int open_flags, + XOpenFlags xopen_flags, + mode_t mode, + LockType locktype, + int operation) { + + _cleanup_close_ int fd = -EBADF; + int r; + + assert(dir_fd >= 0 || dir_fd == AT_FDCWD); + assert(IN_SET(operation & ~LOCK_NB, LOCK_EX, LOCK_SH)); + + /* POSIX/UNPOSIX locks don't work on directories (errno is set to -EBADF so let's return early with + * the same error here). */ + if (FLAGS_SET(open_flags, O_DIRECTORY) && !IN_SET(locktype, LOCK_BSD, LOCK_NONE)) + return -EBADF; + + for (;;) { + struct stat st; + + fd = xopenat(dir_fd, path, open_flags, xopen_flags, mode); + if (fd < 0) + return fd; + + r = lock_generic(fd, locktype, operation); + if (r < 0) + return r; + + /* If we acquired the lock, let's check if the file/directory still exists in the file + * system. If not, then the previous exclusive owner removed it and then closed it. In such a + * case our acquired lock is worthless, hence try again. */ + + if (fstat(fd, &st) < 0) + return -errno; + if (st.st_nlink > 0) + break; + + fd = safe_close(fd); + } + + return TAKE_FD(fd); +} |